President Moon Jae-in of South Korea told President Trump on Thursday that he planned to send a special envoy to North Korea as part of his effort to broker talks between the United States and the North on ending its nuclear weapons program.

President Moon’s office said he talked with Mr. Trump on the phone on Thursday to discuss joint strategies, based upon the discussions Mr. Moon and his aides have held with senior North Korean officials who visited the South last month to attend the opening and closing ceremonies of the Olympics in Pyeongchang.